DietBet

Research shows a healthy weight-loss goal is to drop 4 percent of your body weight over four weeks, so that's what DietBet has you aim for when you toss at least $20 into the pot (amounts vary depending on the bet you choose to join). If you nail it—which you will, obvi—you walk away with a cut of the cash. If you don't, your portion goes to those that do. Bonus: You can join challenges with some of your fave celeb trainers, like Extreme Weight Loss pros Chris and Heidi Powell or Blogilates' Cassey Ho and score extra workout tips.

WellCoin

Rather than winning actual money for reaching your goals, this app operates on a health currency known as wellcoins. You report on all the healthy stuff you do throughout the day (even tiny things, like walking around your office for a quick brain break), and once it's verified, you receive wellcoins in return (the bigger your activity, the more wellcoins you get). Rack up enough coins and you can turn them in to score gear from their online marketplace that's filled with goodies from your favorite health and fitness brands.

Pact

Put your money where your mouth is with Pact, the app that lets you wager a bet each week on how many times you'll reach a certain goal—think: working out four times a week or keeping a daily food log. You "check in" each time you do something that takes you closer to your weekly goal, and the app verifies when you actually achieve it. If you don't, pony up. The pot is communal, so whoever reaches their goals gets to split the cash that everyone handed over.

Charity Miles

This app isn't about putting money in your pocket, but rather about placing it in the hands of those in need. Every mile you bike is 10 cents donated to the charity of your choice and every mile you run is 25 cents. And it's super easy to use: Once you've selected an organization to support, the app automatically tracks the distance you cover, so all you have to do is sweat—no recording required.

HealthyWage

Whether you want to join a team challenge with friends or lose weight solo, HealthyWage ups the ante for at least 90 days (the minimum amount of time you can participate in a bet). Once you submit a 30-second weigh-in video and decide how much to wager, you're off and running. The app calculates your possible winnings based on the specifics of your bet—like how much weight you'll lose over a certain period of time—then tracks your progress and offers up social games to help keep you accountable. Verify your weight in a finish-line video, and if you've met your goal, you can bring home the money through PayPal or Amazon credit—up to $10,000, if you bet big!

Samantha is a writer who is living, eating and sweating her way through NYC. You can find her running half-marathons like it's her job, Instagramming her favorite food and fitness finds or, let's be honest, eating peanut butter straight from the jar.